Prenatal Testing Techniques- Aminocentesis, Sonography, Fetoscopy, Chronic Virus Sampling
Written on February 26, 2009 by steven
Modern technology has enabled medical practitioners to detect health defects in a fetus as early as the 14th to 18th weeks of pregnancy. One common testing procedure, amniocentesis, which is strongly recommended for women over the age of 35, involves inserting a long needle through the mother’s abdominal and uterine walls into the amniotic sac, the protective pouch surrounding the baby. The needle draws out 3 to 4 teaspoons of fluid, which is analyzed for genetic information about the baby. This test can reveal the presence of 40 genetic abnormalities, including Down syndrome, Tay-Sachs disease(a fatal disorder of the nervous system common among Jewish people of Eastern European descent), and sickle-cell anemia(a debilitating blood disorder found primarily among blacks). Amniocentesis can also reveal the sex of the child, a fact many parents choose not to know until the birth. Although widely used, amniocentesis is not without risk. Chances of fetal damage and miscarriage as a result of testing are 1 in 400.
Another procedure, ultrasound or sonography, uses highÂfrequency sound waves to determine the size and position of the fetus. Ultrasound can also detect defects in the central nervous system and digestive system of the fetus. Knowing the position of the fetus assists practitioners in performing amniocentesis and in delivering the child. In 1999, a new three-dimensional ultrasound technique clarified the images and improved doctor’s efforts at detecting and treating defects prenatally.
A third procedure, fetoscopy, involves making a small incision in the abdominal and uterine walls and then inserting an optical viewer into the uterus to view the fetus directly. This method is still experimental and involves some risk. It causes miscarriage in approximately 5 percent of cases.
A fourth procedure, chorionic virus sampling(CVS), involves snipping tissue from the developing fetal sac. CVS can be used at 10 to 12 weeks of pregnancy, and the test results are available in 12 to 48 hours. This test is an attractive option for couples who are at high risk for having a baby with Down syndrome or a debilitating hereditary disease.
If any of these tests reveals a serious birth defect, parents are advised to undergo genetic counseling. In the case of a chromosomal abnormality such as Down syndrome, the parents are usually offered the option of a therapeutic abortion. Some parents choose this option; others research their unborn child’s disability and decide to go ahead with the birth and offer the baby the love and support all children deserve.
Down syndrome A condition characterized by mental retardation and a variety of physical abnormalities.
Human chorionic gonadotropin(HCG) Hormone detectable in blood or urine samples of a mother within the first few weeks of pregnancy.
Trimester A three-month segment of pregnancy; used to describe specific developmental changes that occur in the embryo or fetus.
Embryo The fertilized egg from conception until the end of two months’ development.
Fetus The name given the developing baby from the third month of pregnancy until birth.
Placenta The network of blood vessels that carries nutrients to the developing infant and carries wastes away; it connects to the umbilical cord.
Amniocentesis A medical test in which a small amount of fluid is drawn from the amniotic sac; it tests for Down syndrome and genetic diseases.
Amniotic sac The protective pouch surrounding the baby.
What Do You Think?
What are your most important concerns when considering a health-care practitioner for your or your partner’s pregnancy? What behaviors might you or your partner need to change if you found out that you or your partner were pregnant? Are there any behaviors that you would consider integrating into your lifestyle now that would be of benefit to you or your partner, if you were planning a pregnancy? How much emphasis should be placed on male preconception planning, if any?
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